Update binary search

[BNAndras]

I've added an instructions append to clarify that sorted vectors are being used instead of lists. I've also replaced references to arrays in the test suite. I did some minor formatting and converted a few of the (test-eqv ... #f) tests to the simpler (test-false ...) tests

[github-actions]

This PR touches files which potentially affect the outcome of the tests of an exercise. This will cause all students' solutions to affected exercises to be re-tested.

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[no important files changed]

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